Pressure-equalizing mechanism for cylinders.



G. W. NISTLE. PRESSURE EQUA LIZING MECHANISM FOR GY LINDERS.

APPLICATION FILED MAY 9, 1908.

Patented May 10, 1910.

1 6 m 4 1 w 4 e 9 STATES GEORGE W. NISTLE, OF NORTH MUSKEGON, MICHIGAN,ASSIGNOR OF ONE-THIRD TO EVERETT W. BROOKS AND ONE-THIRD T0 ROBERT L.GIFFORD, OF CHICAGO,

ILLINOIS.

PRESSURE-EQUALIZING MECHANISM FOR CYLINDERS.

Specification of Letters Patent.

Patented May 10, 1914).

To all whom it may concern:

Be it known that I, GEORGE W. NISTLE, a citizen of the United States,residing at North Muskegon, in the county of Muskegon and State ofMichigan, have invented certain new and useful Improvements inPressure-Equalizing Mechanism for Cylinders, of which the following is aspecification.

This invention relates to improvements in pressure equalizing mechanismfor cylinders, and is more particularly intended for saving orconserving part of the force which has heretofore been lost undercertain conditions in driving the piston of fluid-driven engines,notably steam engines.

It is well known that in steam engine practice conditions commonly arisein which the charge of steam admitted to the cylinder or cylinders ofthe engine is insufficient to maintain an effective pressure on thepiston throughout its entire stroke, which condition, of course, meansthat during the interval of no effective pressure the load istransferred to and carried by the flywheel. That is to say, after theadmission of steam has been out ofi the charge in the cylinder willexpand and the pressure on the piston decrease due to such expansion,and cooling and condensation. It frequently occurs that the pressurewill thus be lowered to a point materially below the pressure in theopposite end of the cylinder, 71. e. that pressure against which thecylinder is exhausting, and when this condition occurs it would, ofcourse, be advantageous to equalize the pressure in the cylinder at theopposite sides of the piston, which may be done by providing a suitablycontrolled by-pass leading from one end of the cylinder to the other,or, in case the engine be non-condensing, might be practicallyaccomplished by admitting atmospheric pressure behind the piston. Ineither event the piston would be thus relieved from advancing against anunnecessary and non-effective pressure.

It is the salient object of the present invention, therefore, to provideautomatic mechanism for equalizing, or tending to equalize, thepressures upon the opposite sides of the piston of a fluid-actuatedengine, when, during the advance of the piston, the pressure on thedriving side falls below that at the opposite side.

The invention consists in the matters hereinafter described, and moreparticularly pointed out in the appended claims.

In the drawingsFigure 1 is a perspective view of a steam engine of thesingle cylinder type, showing the cylinder thereof equipped with apreferred embodiment of my invention; Fig. 2 is an axial sectional viewtaken in a horizontal plane of one of the valve casings controlling aby-pass leading from the pressure to the exhaust side of the engine;Fig. 3 is another axial sectional view taken in a plane at right anglesto that of Fig. 2; Fig. 4: is a transverse sectional view taken on line4l4c of Fig. 3 and looking in the direction of the arrows.

Referring to the drawings, 1 designates as a whole a steam engine, inwhich 2 designates the cylinder, 8 the connecting rod, 4 the crank shaftand 4: the fly-wheel; these parts being of usual construction. Theengine shown in this instance is of the double acting type, providingfor the admission of steam at each end of the cylinder and correspondingexhaust therefrom, but the invention is applicable to engines of thesingle acting type.

5 designates the exhaust pipe which connects with a chest or valvecasing 6, the lat ter containing any suitable valve mechanism, andexhaust ports controlled thereby, whereby each end of the cylinder isalternatively placed in communication with said exhaust pipe 5.

7 designates the steam inlet pipe which likewise communicates throughsuitable valve controlled ports within the casing 6 with the oppositeends of the cylinder.

Describing, now, the mechanism relating more particularly to the presentinvention, 8 designates a pipe connected at one end with the exhaustpipe 1 and at its opposite end provided with two branches 9 and 9, whichbranches connect with the respective ends of the steam cylinder throughvalve mechanisms 10, 10, and expansion branch pipes 11, 11. The twobranch pipes 9 and 9' serve as alternative by-passes leading from thecorre sponding ends of the cylinder through the pipe 8, exhaust pipe 5,and back to the opposite end of the cylinder.

Describing the details of construction of one of the valve mechanisms 10and 10, both being alike, and referring to Figs. 2, 3 and 4, 12designates as a whole a thick walled cylindric-shaped valve casingprovided at one end with a detachable end closure 13 which has an axialcylindric plug-like extension let which fits into the main bore of thevalve casing. The opposite end of the valve casing is axiallycounterbored, as indicated at 15, to receive the end of a closelyfitting valve stem 16, and similarly the plug member 14 is axiallybored, as indicated at 17, to receive the opposite end of the valve stem16. The ends of the valve stem fit these bores within which they extendwith such accuracy as to act as pistons under certain conditions, aswill hereinafter be described. Upon the intermediate portion of thevalve stem is fixed a piston member 18 which accurately fits the mainbore of the casing, and the latter bore is annually enlarged to providetwo port chambers 19 and 20, communication between which is controlledby the piston 18. The piston 18 is shown in its normal position in whichit lies chiefly within the port chamber 19 but extends into theintermediate portion 21 of the main bore of the cylinder sutficiently toclose communication between the chambers 19 and 20. The chamber 19communicates through a port 22 and extension pipe 11 with one end of thesteam cylinder, while the port'chamber 2O communicates through a port23, branch pipe 9 or 9 and connecting pipe 8 with the exhaust pipe 5.Obviously during the principal part of the advance stroke of the pistonof the main cylinder, the valve piston 18 of the valve mechanism whichcommunicates with that end of the cylinder will be forced from the portchamber 19 toward the chamber 20, its advance in this direction beinglimited by the end of the valve stem ap proaching the end of thecounterbore or chamber 15, and being cushioned by the steam in thelatter. Should the pressure in that end of the cylinder with which thechamber 19 communicates fall below the exhaust pressure, and thereforebelow the pressure in the chamber :20, which is in direct communicationwith the exhaust, it will be obvious that the piston 18 will be shiftedtoward its opposite limit of movement, and in so shifting will becarried fully into the chamber 19 and thus place the chambers 20 and 19in communication, which thus places the end of the main steam cylinderin com munication with the exhaust pipe and permits such inflow ofexhaust steam as will equalize the pressures in both sides of thepiston. The valve mechanism is, therefore, essentially a check-valve,though of special construction. v

In order to provide for the cushioning of the piston valve and its stem,a steam passage 24: of restricted size leads from the chamber 19 throughthe body of the casing to, and communicates with, the chamber 15 at apoint slightly removed from the outer end of the latter chamber, andsimilarly a passage 25 leads from the chamber 20 to, and communicateswith, the chamber 17 at a point slightly removed from the outer end ofthat chamber. Under normal conditions the chambers 15 and 19 will be incommunication and therefore under the same pressure, and similarly thechambers 17 and 20 will be in communication and under the same pressure.As the piston valve moves in one direction or the other it will cut oiithe passage leading into the cushioning chamber into which it isadvancing, and during the remainder of its advance cushion against thetrapped steam. This trapped and compressed steam will, of course, aid inreturning the piston valve to its normal intermediate position. In thisconnection, it is to be noted that the arrangement by which the chamber19 is normally in communication with the chamber 15, and the chamber 20normally in communication with the chamber 17, makes of the piston valvewith its stem as a whole a differential piston, since the pressure ineach cushioning chamber opposes the movement of the piston in thedirection in which it tends to move under the action of the port chamberwhich communicates with that cushioning chamber.

While I have herein shown and described what I deem to be a preferredembodiment of the invention, yet it is to be understood that in thebroader sense the invention is not limited to the particular arrangementor construction of mechanism shown and described.

I claim as my invention:

1. In a motive fluid engine, the combination with a cylinder and pistontherein, of a conduit communicating directly with the driving side ofthe piston head at one end and at its other with the exhaust side of theengine, and a pressure operated check valve mechanism interposed in andcont-rolling said conduit comprising a valve member, one side of whichis subject to the varying working pressure in the cylinder and the otherside of which is subject to the pressure from the exhaust side of theengine whereby the valve is controlled by cylinder pressure only and isshifted to open the conduit to admit fluid to the driving side of thecylinder from said other source whenever the pressure on the drivingside of the piston head falls below the pressure on the exhaust side ofthe conduit.

2. In a motive fluid engine, the combination with a steam chest, of acylinder and a piston therein, a conduit communicating at one enddirectly with the driving side of the piston head independently of anyconnection with the steam chest, and at its other with the exhaust sideof the engine, and a pressure operated check valve mechanism openableinwardly and operable to admit an equalizing fluid to the cylinder fromthe exhaust side of the engine whenever the pressure on the driving sideof the piston head falls below the pressure in the exhaust side of theengine.

3. In combination, a valve casing, a piston reciprocating therein anddividing said casing member into two chambers, a cushioning chamber ateach end of the piston rod sealed from communication with the adjacentmain chamber, main conduits leading into said main chamber on oppositesides of the piston head and other conduits leading from the respectivesides of the main chamber to the respective cushioning chambers, saidlatter conduits being cross connected so that each afi'ords constantcommunication between this cushioning chamber and that part of the mainchamber remote therefrom.

i. In a motive fluid engine, the combination with a cylinder and pistontherein, of a conduit communicating directly with the driving side ofthe piston made independent of any connection with the steam chest, andalso communicating with another source of pressure, and a check valvemechanism openable inwardly and operable to admit an equalizing fluid tothe cylinder.

GEORGE W. NISTLE.

Witnesses:

W. C. NIsTLE, O. SQPLAGE.

